SE430222B - PROCEDURE FOR STIRRING AND DEVICE FOR PREPARING THIS - Google Patents

Description

20 25 30 fvesàovoffn-s in 2 phase difference. In this way, the two agitators can cooperate in such a way that a sufficiently high flow rate and a sufficiently efficient agitation in the sump are obtained.

The invention also relates to a device for carrying out this method, comprising a continuous casting machine with a mold and at least two electromagnetic, two-, three-phase or multi-phase stirrers for stirring the non-solidified portions of the casting strand.

In a preferred embodiment, one or both agitators are designed so that asymmetric agitation is obtained, i.e. some turbulence is obtained from the agitator, for example so that the current in one phase to at least 10% deviates from the corresponding in at least one adjacent phase or that the phase coils on correspondingly are asymmetrically designed. Such an asymmetric stirrer is described in connection with the procedure shown in Swedish patent application 7811562-3.

Stirring of the non-solidified portions in a casting strand is previously known in various forms. It is known, among other things, to stir these parts with an electromagnetic stirrer across or along the casting direction in one or more places. One of the reasons for this is that you want to prevent lacing, so-called mini-ingots, and victories in the finished substance and you want as smooth a solidification process as possible; You also want to avoid so-called white bands, and a solution to this problem is the_asymmetric stirring. The present invention involves a further development of this problem solution.

The invention is further exemplified in the accompanying figures, of which figure 1 shows two stirrers with pronounced poles and figure 2 two stirrers of another kind.

Both of these are applied to casting strings of the slab, bloom or billet type.

When, for example, discharge from a casting mold (not shown) of a slab blank 1 (see arrow), the blank is discharged by means of rollers 8, 11, placed in the case shown between the distinct poles of two stirrers 2, 3. The rollers between the stirrers should of course be made in magnetic material to prevent the field from being shielded or short-circuited. The stirring direction of the two stirrers 2, 3 must be the same, see the double arrows in the molten part 9 of the substance 1. The stirring frequency at the slab frequency is 0-1Ö Hz, at bloom stirring 10-30 Hz and at billet stirring 50-60 Hz, and in some cases one can even imagine 10 -20 7907040-5 round substances. The agitators 2, 3 are suitably placed opposite each other at the wide sides of the slab blanks and are arranged to work synchronously, which means that the field emanating from agitator 2 is sucked into agitator 3, and suitably the phase difference of 1800 should be maintained. To obtain the turbulence in the agitation, the agitators are made in a known manner for asymmetric agitation and the asymmetry is correspondingly amplified by this coupling.

Figure 2 shows corresponding stirrers with non-pronounced poles 7, 4, and feed rollers 5, 6 are placed between the stirrers and the string 10, the rollers between the stirrers and the string should be made of non-magnetic material, but of course the stirrers can also be placed between rollers. if possible with regard to the current construction.

The stirrers as above can also be supplemented with other pairs of stirrers or with individual stirrers, and the stirring direction can be transverse or along the casting direction, possibly also at an acute angle thereto.

In the method according to the invention, the casting string 1, 10 is fed in the direction of the arrow between the two opposite stirrers, see the double arrows, and a synchronous stirring is obtained with the asymmetry amplified, and an excessively low flow rate in the sump 9 is avoided.

The method and device as above can be varied in many ways within the scope of the following claims.

Claims (3)

790704045 PATENT CLAIMS A method of stirring the non-solidified portions of a casting strand, coming from a continuous casting machine, the strand being formed in a mold and stirring being carried out by means of at least two electromagnetic stirrers, characterized in that the melt is known per se is stirred by means of two electromagnetic stirrers (2, 3), placed substantially opposite each other at the casting string (1) or in the mold, opposite each other at each of the wide sides of the blank, and that the field from the two stirrers (2, 3, Ä, 7) is given the same direction of travel field and such a mutual phase difference that when the field from a pole a stirrer has a maximum, directed_to the casting string, the field from opposite pole in the second stirrer has a maximum, directed from the casting string, i.e. the two stirrers are given 1800 mutual phase difference. Device for carrying out the method according to claim 1, comprising a continuous casting machine with a mold and at least two electromagnetic, two-, three-phase or multi-phase stirrers (2, 3, H, 7) for stirring the non-rigid the portions (9) of the casting string, characterized in that at least two stirrers are placed opposite each other at each of the wide sides of the blank (1), and that the feeding of the stirrers (2, 3, Ä, 7) is arranged to take place "with the same migration field direction and in such a way that the field receives a pole in one stirrer has a maximum directed towards the casting string when the field from the opposite pole in the other stirrer has a maximum, directed from the casting string. Device according to claim 2, characterized in that the stirrers (2, 3, 4, 7) are designed for asymmetric stirring, for example so that the current in a phase to at least 10% deviates from the corresponding in at least one adjacent phase or that the phase coils are correspondingly asymmetrically designed.